Chronic Fluoride Exposure and the Risk of Autism Spectrum Disorder

by Anna Strunecka * andOtakar Strunecky
6. Conclusions

The rise in the ASD prevalence in countries with water fluoridation as well as in endemic fluorosis areas supports a view that F is an important environmental factor in the ASD etiopathogenesis. Our suggestion of the important role of F in the ASD etiopathogenesis is supported by the observation that a high ASD rate is found in countries with a high occurrence of dental fluorosis.

F neurotoxicity has been demonstrated in many laboratory studies with cells and animals, as well as in human epidemiological studies. We present evidence that F induces mitochondrial dysfunction, oxidative stress, inflammation, and immunoexcitotoxicity. There is a link between a known effect of F on melatonin synthesis in the pineal gland and the finding that melatonin synthesis is significantly reduced in ASD. Moreover, understanding F-induced pathways in the ASD etiopathology may lead to novel treatments. All these F-induced symptoms could evoke several disruptions of the brain development, alter neurotransmission and hormonal regulations, deficits in social interactions and induce repetitive, stereotypic interests, and behaviors resulting in ASD.

At present, there is a divergence between public health practice of water fluoridation, which is regarded as valuable and safe for reducing dental caries, and current scientific evidence, which indicates that F is a neurotoxin disturbing prenatal as well as postnatal brain development, eroding intelligence, and behavior. The potential neurotoxicity associated with exposure to F, which has generated controversy about community water fluoridation, remains unclear. In the recent Canadian study, maternal exposure to higher levels of F during pregnancy was associated with lower IQ scores in children aged 3 to 4 years [67]. These findings support the possible need to reduce F intake during pregnancy. Intellectual disability is present in 65%–75% of individuals with a diagnosis of autistic disorder and in 30%–55% of all ASD [3].

F is not an essential nutrient as no physiological function can be defined for which F is required. The presence of trace amounts of Al3+ strongly potentiates the neurotoxic effects of F. AlF4− can trigger the pathological symptoms of ASD at concentrations several times lower than those for F acting alone. In synergy with Al3+ every concentration of F might be dangerous for the developing brain. Our review suggests that the reduction of F exposure in daily life might be an efficient way to prevent an ASD epidemic soon. Monitoring of the ASD prevalence in children born after the removal of F from drinking water will provide relevant information for our hypothesis.